<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<style type="text/css">
		.radius {
			width: 50px;
			height: 50px;
			line-height: 100px;
			display: block;
			text-align: center;
			background-image: radial-gradient(200px at 50px 0px, #fff 50px, #4169E1 50px);
		}
	</style>

	<body>
		<span class="radius"></span>
		<code>function abc(){}</code>
	</body>

</html>